<?php $a = null;
  $a = $a + 1;
  $a = $a - 1;
  $a = $a * $a;
  $a = $a / $a;
  $a = $a . $a;
  $a = 'hello' . ' world';
  $a = "hello" . " world";
  $a = 'hello$a';
  $a = "hello$a";
  $a += $a;
  $a -= $a;
  $a *= $a;
  $a /= $a;
  $a .= $a;
  $a = $a && $b & $c;
  $a = $a || $b | $c;
  $a &= $a;
  $a |= $b;
  $a = $f ^ $g;
  $a ^= $g;
  $a = ($b * $c) / (($d * $e) ^ $f);
  $a = !!$a;
  $a /* c */
  = /* c */
  $a /* c */
  / /* c */
  $a; ?>